1. Field of the Invention
The present invention relates to a method and apparatus for producing turbine blade roots, and, more particularly, to a method for producing turbine blade roots by a combination of wire electric discharge machining and subsequent peening of the machined portions.
2. Description of the Related Art
As is well known, the manufacture of high precision turbine blades and the corresponding turbine blade roots is a highly exacting operation. Tolerances are particularly critical for both components at the point at which the turbine blades are fitted onto turbine rotors. There are a wide variety of designs of turbine blades and roots, but for all varieties, a major problem has always been the extreme stresses to which the blade roots are subjected during operation of the turbine. Therefore, during manufacture, turbine blade roots must be precision cut to conform with strict requirements for fit, while maintaining durability.
Conventionally, a turbine blade root has been formed by a transfer line type cutting process having multiple operations, including broaching. Such a process requires extensive set-up time for each operation; for broaching alone, the set-up time is fifteen hours. In addition, the tools required for each operation are very expensive. Moreover, as dedicated specialized tooling is required for each type of blade root to be manufactured, tooling time alone for each blade root design can require 16 to 30 weeks of lead time.